1. Field
The present application relates generally to the operation and design of wireless communication systems, and more particularly, to a system for better service reselection when on other than the most preferred system.
2. Relevant Background
When a Mobile Station (MS) has acquired a system that is other than the Most Preferred in a particular region, the MS searches for More Preferred systems in a process known as Better Service Reselection (BSR). For example, the MS has a Preferred Roaming List (PRL) that identifies and prioritizes the various networks that the MS may encounter. The MS can search this list to determine if it is operating on the Most Preferred system since traffic (e.g. voice, packet data, SMS) sent or received on a system identified as Less Preferred (i.e. not the Most Preferred) often represents a higher cost to the Home operator for the MS, and possibly to the end-user. In addition, the quality experienced by the user may be lower on a Less Preferred system.
The current algorithm for BSR uses a configurable period timer, and a search bound timer. Whenever the period timer expires, the MS performs BSR until either: better service is found; the list of channels to search is exhausted; or the search bound timer expires.
Unfortunately, the current algorithm exhibits several problems. For example, between expirations of the period timer, the MS is not searching for better service. If the MS is on a Less Preferred system and has moved back into the coverage area of the Most Preferred system, it will not acquire this system until the next expiration of the timer. Another problem with the current algorithm is power consumption. Searching for service is battery-intensive and the current algorithm requires the MS to “wake-up” based on the period timer to initiate a search, during what may otherwise have been a battery-saving “sleep” period. This results in an increase in power consumption for the device. Still another problem with the current algorithm is that while the MS is searching for better service, the MS may not be monitoring the paging channel on the currently acquired (Less Preferred) system. Thus, paging messages directed at the MS (e.g. for voice calls or SMS messages) sent by the Less Preferred network during this search time may not be received at the MS.
Therefore, it would be desirable to have a system for better service reselection that overcomes the problems associated with conventional systems described above.